Ladder



Feb. 11, 1969 w. BERGER 3,426,867

LADDER Filed June 9, 1967 INVENTOR. LEWIS W. BERGER United States Patent 3,426,867 LADDER Lewis W. Berger, Louisville Ladder C0., 1163 Algonquin Parkway, Louisville, Ky. 40208 Filed June 9, 1967, Ser. No. 645,014 US. Cl. 182-46 6 Claims Int. Cl. E06c 1/00, 7/08; A62b 3/ 00 ABSTRACT OF THE DISCLOSURE A ladder having a non-metallic side rail, or a side rail with insufficient resistance to torque for conventional methods of ladder assembly, with an opening therethrough and a rung extending into the opening. A pair of beads are formed in the rung to sandwich the rail therebetween and secure the rung thereto. An annular element is disposed between the rail and at least one of the beads. The element has projections to engage the bead and the rail to prevent rotation of the rung relative to the rail.

Background of the invention This invention relates generally to ladders and, more specifically, to an improved means for securing a rung to a thin or non-metallic side rail of a ladder. The term ladder as used herein includes scaffold frames wherein rung-to-rail connections are employed.

It is frequently desirable to utilize a ladder having side rails formed of material other than metal. For example, when the person using the ladder is working around electrical apparatus it is desirable that the ladder side rails be made of electrically insulative material. A concurrent desirable aspect is, of course, that the ladder be sufficiently light weight to enable easy movement. Light weight is achieved by using relatively thin material to form the side rails. One material which has been found to meet these requirements is glass fiber formed into an I-beam or C-channel configuration. Since the insulative side rails provide adequate electrical insulative characteristics, between the workman and the ground, the rungs may be made of electrically conductive material. The most suitable material for the rungs has been found to be aluminum and, in fact, the rungs normally used in aluminum ladders can be employed with glass fiber side rails.

A problem has been encountered in suitably securing the aluminum rungs to the glass fiber side rails. For example, it has been found that conventional crimping of the rung to the side rail will eventually cause the glass fiber material to break down thus allowing the rung to rotate, about its axis, relative to the side rail. This weakens the ladder and makes it unsafe to use. Thus, it would be advantageous to provide an improved means for securing a metallic rung to the non-metallic side rails of a ladder "which would minimize the possibility of the rung eventually working loose, and further minimize local buckling of the side rails at the connection point of the rung.

Summary of the invention Briefly stated, in accordance with one aspect of the present invention, a ladder is provided and has at least one elongated side rail with an opening therethrough. A rung extends through the opening. First and second peripheral beads are formed on the rung. At least one generally annular element is disposed about the rung between the side rail and at least one of the peripheral beads. The generally annular element has projections in contact with the side rail and the peripheral bead. The beads serve to sandwich the generally annular element and the side rail together whereby the rung is secured to the side rail and the projections prevent movement of the rung relative to the side rail.

Brief description of the drawings While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention will be better understood from the following description of the preferred embodiments taken in connection with the accompanying drawing, in which:

FIGURE 1 is a fragmentary perspective view of an extension ladder employing the present invention;

FIGURE 2 is a sectional view of one side rail of the ladder of FIGURE 1 showing in detail the connection between a rung and the side rail;

FIGURE 3 is a view taken along line 3-3 of FIG- URE 2;

FIGURE 4 is a view similar to FIGURE 2 showing a modified form of the present invention;

FIGURE 5 is a plan View of one element of the present invention; and,

FIGURE 6 is an exploded view of the modified form of FIGURE 4 prior to assembly.

Description of the preferred embodiments Referring now to the drawing, and initially to FIGURE 1 thereof, an extension ladder 10 is illustrated and has a first section which comprises a pair of side rails 11 interconnected by a series of rungs 12. Ladder 10 also includes a second section having a pair of side rails 13 interconnected by a series of rungs 14. The two sections of ladder 10 are secured together, either in an extended relationship or a retracted relationship, by a pair of rung locks 15 which are secure to side rails 13 and are adapted to lock onto rungs 12 in a manner well known in the extension ladder art.

As mentioned above, the present invention is particularly directed toward an improved means to interconnect aluminum rungs to non-metallic side rails, the side rails being formed from such non-metallic material as glass fiber, or to side rails of relatively thin material. Rungs 12 and 14 may be of conventional tubular aluminum construction ordinarily found in a ladder having aluminum side rails. Side rails 11 and 13 are formed from a nonmetallic material such as glass fibers. It should be noted that although side rails 11 and 13 are shown in the drawing as having an I-beam configuration, the present invention is equally applicable to other side rail configurations such as, for example, a C-channel configuration.

Referring now to FIGURE 2, there is shown one embodiment of the present invention. The side rail 11 is in the form of an I-beam having flanges 16 and 17 interconnected by a relatively thin web 18. Web 18 has an opening 19 through which a portion of rung 12 extends. Rung 12 has a first peripheral bead 20 formed therein and a second peripheral bead 21 spaced from bead 20. A first generally annular element 22 is disposed between bead 20 and web 18. Similarly, a second generally annular element 23 is disposed between web 18 and bead 21.

Elements 22 and 23 may be identical and, may be formed from any suitable material which will serve the function hereinafter described. It can be seen that each of elements 22 and 23 has a plurality of projections 24 on each fiat surface thereof. Projections 24 engage the surface of web 18 and the adjacent surface of beads 20 and 21 so that, as bead 21 is formed to sandwich elements 22 and 23 and web 18 between beads 20 and 21 to secure rung 12 to side rail 11, the engagement will prevent movement of rung 12 relative to web 18.

It has been found in practice that elements 22 and 23 may suitably be formed from the same material as rung 12, i.e., sheet aluminum. The most eflicient way to produce elements 22 and 23 is to extrude a strip wherein projections 24 are formed during the extrusion, and then punch the elements from the strip while at the same time punching a central opening of slightly greater diameter than the outer diameter of rung 12 so that elements 22 and 23 can slip over rung 12 in the manner illustrated in FIGURE 2.

Referring now to FIGURE 4, a modification of the system of FIGURE 2 is illustrated and involves a modified second peripheral bead 21a. Since the remaining elements of the embodiment of FIGURE 4 are identical to those in FIGURE 2, they have been given identical reference numerals. Peripheral bead 21a differs from peripheral bead 21 in that it is formed by flaring the end of rung 12 radially outwardly and then radially inwardly to form a bead having a generally U-shaped configuration. Although it has been found in practice that head 21 of FIGURE 2, wherein the bead is formed simply by flaring the end of rung 12 radially outwardly, provides the necessary structural characteristics, a problem in assembly has been encountered which is solved by the U-shaped bead 21a. The problem is that when rung 12, elements 22 and 23, and web 18 are all loosely assembled prior to the forming of the second peripheral bead, when the second peripheral bead is of the type shown as 21 in FIGURE 2, the amount of material of rung 12 extending beyond element 23 is such that it is difficult to maintain element 23 in position while the tool is being brought into operative position to form the bead 21. Thus, by forming a U-shaped bead 21a, more material is available to maintain element 23 in position prior to forming the bead.

With respect to the method of assembly, reference is made to FIGURE 6 wherein the elements are shown in exploded fashion. It can be seen, that bead 20 is formed in rung 12 prior to the assembly of elements 22 and 23 and side rail 11. Assembly is effected by slipping element 22 over rung 12 until it contacts head 20, then passing rung 12 through opening 19 in web 18, then slipping element 23 over that portion of rung 12 which extends through and beyond web 18. After this has been accomplished, a tool 26 is brought into contact with the end of rung 12 to form the second peripheral bead by flaring the end of rung 12 radially outwardly to an extent whereby elements 22 and 23 and web 18 are all firmly sandwiched together and projections 24 engage the beads and web 18. To form peripheral bead 21a as shown in FIGURE 4, tool 26 is configurated to further deform rung 12 radially inwardly to form a bead having a generally U-shaped configuration. Rung 12 is, of course, suitably held by a fixture (not shown) during the time that tool 26 is forming the second peripheral bead.

It should be noted that the diameter of elements 22 and 23 preferably exceed the diameter of beads 20 and 21 or 21a to thus distribute the sandwiching force over a greater area of web 18.

When aluminum rungs are employed with glass fiber side rails in an extension ladder, it has been found that the sliding engagement between the side rails and the rungs, during extension and retraction of the ladder, causes a wearing away of the rung. To overcome this problem, the present invention further provides a member 27 secured to rung 12, adjacent bead 20, by means of rivets 28. Side rails 13 slide on member 27 this protecting rungs 12. A standard, low grade stainless steel serves suitably as member 27.

As will be evident from the foregoing description, certain aspects of the invention are not limited to the particular details of construction of the examples illustrated, and it is contemplated that various other modifications or applications will occur to those skilled in the art. It is therefore intended that the appended claims shall cover such modifications and applications as do not depart from the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A ladder comprising:

(a) at least one elongated side rail having an opening therethrough,

(b) a hung extending through said opening,

(c) a first peripheral bead formed on said rung,

(d) a flat annular first element having opposed flat surfaces with projections formed on each flat surface by extrusion,

(e) said first element being disposed about said rung between said first bead and said side rail,

(f) a second peripheral bead formed on said rung,

and

(g) a fiat annular second element having opposed fiat surfaces with projections formed on each fiat surface by extrusion,

(h) said second element being disposed about said rung between said second bead and said side rail,

(i) the diameter of each of said first and second elements being substantially greater than the diameter of each of said first and second beads,

(j) said beads serving to sandwich said annular elements and said side rail together whereby said rung is secured to said side rail and said projections prevent movement of said rung relative to said side rail.

2. The invention of claim 1 wherein said side rail is formed from glass fibers and said rung is formed from aluminum.

3. The invention of claim 1 wherein said generally annular elements are extruded from aluminum.

4. The invention of claim 1 further comprising a member secured to said rung adjacent said first peripheral bead to protect said rung against sliding engagement with a second side rail.

5. A ladder comprising:

(a) at least one elongated side rail having an opening therethrough,

(b) a rung of generally circular cross section extending through said opening,

(c) a first peripheral bead formed on said rung,

(d) a second peripheral bead formed on said rung,

and

(e) a flat annular element disposed about said rung,

between said side rail and at least one of said peripheral beads,

(f) said flat annular element having opposed fiat surfaces with projections formed on each flat surface by extrusion and having a diameter substantially greater than the diameter of either of said first and second peripheral beads,

(g) said beads serving to sandwich said annular element and said side rail together whereby said rung is secured to said side rail and said projections prevent movement of said rung relative to said side rail.

6. The invention of claim 5 further comprising a member secured to said rung adjacent one of said peripheral beads to protect said rung against sliding engagement with a second side rail.

References Cited UNITED STATES PATENTS 845,639 2/1907 Herri-man 20--92 1,977,602 10/1934 Olson 1Sl-35 2,228,525 1/ 1941 Lundskow 182-207 3,327,385 6/1967 Shaver 182228 FOREIGN PATENTS 468,382 11/ 1928 Germany. 780,393 1/1935 France.

REINALDO P. MACHADO, Primary Examiner.

US. Cl. X.R. 

